Anti-drive mechanism for rotary aircraft control

A rotary aircraft, comprising:

• an airframe;
• a main rotor assembly;
• a gearbox and drive shaft to drive the main rotor assembly;
• a pilot control input;
• a swashplate assembly to translate pilot control inputs to motion of the main rotor assembly, the swashplate assembly comprising:
• a rotating ring to engage the main rotor assembly and to rotate with the drive shaft;
• a non-rotating ring mechanically coupled to the rotating ring and rotationally decoupled from the rotating ring, wherein the non-rotating ring does not rotate with the rotating ring and the drive shaft;
• a tilt ball mechanically coupled to the non-rotating ring to prevent the tilt ball and non-rotating ring from rotating relative to one another;
• and
• an unpinned key-and-slot system on an unsplined mechanical interface between a contact surface of the tilt ball and the gearbox, comprising a plurality of keys disposed equidistantly around a circumference of the gearbox, the plurality of keys having a long axis along a height of the gearbox with a length longer than a height of the tilt ball, and a short axis along a circumference of the gearbox having a width substantially shorter than the long axis, and a plurality of slots disposed on the tilt ball having position and size to securely enclose the plurality of keys.